Apparatus for the separation of platinum and gold by volatilization



Dec. 1, 1964 E. R. WOLCOTT 3,159,703

APPARATUS FOR THE SEPARATION 0F PILA'IIIIUIVI AND GOLD BY VOLATILIZATIONFiled Oct. 26, 1961 I INVENTOR. fDSO/VJP. 11/01. 0077 Airmen/0 UnitedStates Patent M 3,159,703 APPARATUS FQR THE SEPARATKGN Gi PLATT- NUM AND(HELD BY VGLATTLHZATEQN Edson it. Wolcott, 917 Crenshaw Blvd, LosAngeles 19, Qalif. Filed Oct. 26, 19rd, Ser. No. 147,8tlt) 1 Claim. (Qt.ass-19 In my copending application, Serial No. 858,268, filed Dec. 8,1959, now matured into Patent No. 3,049,422, issued Aug. 14, 1962, ofwhich this application is a continuation-in-part, I have disclosed mynew and useful process for the separation of platinum and gold fromfinely divided ores and sands by volatilization, and my presentinvention pertains primarily to apparatus adapted for efiiciently andcontinuously carrying out my aforesaid process.

The use of this new apparatus is not restricted to the carrying out ofthe process above indicated and may have other uses as well.

The apparatus and its advantages will be more fully understood andappreciated by referring to the accompanying drawings and the followingdetailed description.

The single figure of the drawings is a partially diagrammatic elevationof apparatus embodying this invention,

in which the furnace is shown in sectional elevation, and the tank wherethe vapors containing the platinum and gold compounds are condensed isbroken away to show the jet pump and other internal connections.

Referring to the drawings, the apparatus shown is composed of a tubularfurnace iii which is set in a substantially horizontal position and iscylindrical in form. It is composed of an inner tubular retort 11 whichis preferably formed of clay or other ceramic material and has a helicalgroove 12 on its outer surface in which an electrical heating element 13is wound. An outer metal furnace shell 14 of substantially largerdiameter surrounds the retort, and the space between the furnace shelland the retort is filled with insulation, as shown at 15.

Within the retort 11 and extending axially through it is an anger feed16 which is helical in form and is rotatably mounted in bearings 20, 21on a central axis 17 which is coaxial with the retort 11. The bearings20, 21 are mounted in end plates 22, 23 of the furnace. The auger 16 isrotated by motor 24 which includes suitable reduction gears 25 and 26 toturn the auger very slowly, for example at the rate of revolutions perminute. The ore to be treated is contained in a hopper 39 which may beprovided with a vibrating mechanism 31 to insure that the finely dividedore or sand flows freely from the hopper 3h downwardly through the feedpipe 32 into the inlet end of retort ill. The feed pipe extends throughthe end plate 2.2, as shown in the drawings. The ore is then advancedslowly through the retort by the auger feed 16. The auger feed may fitloosely in the retort ll. or may have holes 18 so that gas and vaporsmay pass through the retort but come in contact with the ore.

Steam is preferably introduced into the retort near the inlet endthrough a pipe 35 from a glass container or boiler 36 which is heated byelectric heater 37. The introduction of steam is not an essentialfeature of the process and may be omitted.

Chemical in vapor form is fed through pipe 4% to the inlet end of theretort 11 from a glass container 41 which contains hydrochloric acid(HCl), which is fed at a predetermined rate from funnel 42 throughcontrol valve 45 and pipe 46, in liquid form, A predetermined amount ofnitric acid (HNO is also fed to the glass container 41 from funnel 43through control valve 47 and pipe 48, in liquid form. The rate at whichthe two acids are fed to the glass container 41 is determined by theproportion 3,159,703 Patented Dec. 1, 1964 of the desired acids whichare united in the container 41 to form aqua regia, the usual proportionbeing three parts of hydrochloric acid to one part of nitric acid. Theglass is warmed by an electric heater 44 and the vapors, produced bywarming the acid mixture, which consist of nitrosyl chloride andchlorine flow through the retort 11 and are brought into intimatecontact with the finely divided ore being advanced through the retort bythe auger feed 15. As the ore is being treated, as above indicated, heatis applied to the ore from the retort 11 by the electric heater 13 whichsurrounds the retort, and I prefer to use a temperature as applied tothe ore of about 400 F. I have found that utilizing an ore or sandsground to about 20 mesh gives satisfactory results in the process.

The ores to be treated contain small percentages of platinum and goldcompounds, and the nitrosyl chloride plus chlorine vapors coming incontact with the ore under the heated conditions existing in the retort11 volatilize out the plitinum and gold by forming volatile compoundstherewith. The vapors of these volatile compounds then flow outwardlythrough pipe Stl and are drawn therethrough by a jet pump 51 into thereceiving tank 55. The jet pump comprises a venturi nozzle 56 and theinlet pipe 51') through which the platinum compound vapors are drawn. AKOH or other suitable caustic solution is maintained in a container 59and is forced through pipe so into the pipe 58 and through venturinozzle 56 by a pump 62 operated by a motor 63. The container 55% isconnected to the bottom or" the tank 55 by pipe 61 and the solutioncontacts the gold and platinum vapors at the jet pump and absorbs them.It is recirculated through the container 5? and the pipes 69 and 5S andis consequently concentrated in the tank 55. As the gases mix with theKGH solution in the jet pump 51, the platinum is precipitated. Any goldwhich comes over in the vapors is held in solution and is precipitatedseparately at a later time.

The venturi nozzle through which the KGH solution flows produces avacuum up to several inches of water and therefore draws the vaporousproduct from the retort.

The ore from which the platinum and gold have thus been separated byvaporization is discharged at the outlet end of the retort through pipe70 and is accumulated in a container 71 which is adapted to receive thetailings. The tailings are broken up, if caked, and are forced throughthe pipe '76 by an anger feed 72 driven slowly by motor 73 and reductiongears 74.

The operation is as follows:

Finely divided particles of ore or sand are introduced into the hopper3% which is vibrated by vibrator 31 so that they pass freely downthrough pipe 32 and enter the inlet end of the retort 11 and are carriedgradually forward through the retort from the inlet end by the augerfeed 16. At the same time nitrosyl chloride and chlorine are introducedthrough pipe 4t and preferably steam is introduced through pipe 35 intothe retort at the inlet end and are mixe with the finely divided ore,the auger feed acting as a mixing device as well as a means of feedingthe ore forward.

The nitrosyl chloride plus chlorine volatilizes any platinum, platinumcompounds or gold which are contained in the ore. These vapors passoutwardly through pipe 50 and after being mixed with caustic in tank 55are recirculated through pipe 58 into the tank 55 by the jet pump 51, ashereinbefore explained.

A trap 76 of glass or other transparent material is connected to thepipe 5i so that the operator may make a visual observation of the vaporspassing through the pipe 55?.

A caustic solution, preferably KOH, is placed in the tank 59 and byreason of the pump 62 is circulated from 3 the tank 59 through pipes 60and 58 and is then discharged downwardly through the venturi nozzle 56of the jet pump 51. The pipe 50 enters the jet pump so that the streamof caustic will draw the vapors into the tank 55 and at the same timemix the vapors thoroughly with the caustic.

When the vapors contact the caustic solution, platinum is precipitatedand may be removed at the end of the run or continuously by drawing otffrom tank 55 through outlet pipe 80, control valve 81 and into container82. The precipitate solution may be withdrawn from container 82 throughvalve 86.

The tailings of the ore, from which the platinum and gold have beenremoved by volatilization, may contain iron oxide or other compoundswhich remain in solid condition, because the temperature of the retortis not sufiiciently high to break them down, and moreover they do nottend to form volatile chlorine compounds because of the strong oxidizingetiect of the nitrosyl chloride.

To avoid the KOH solution in tank 55 becoming saturated, I prefer to adda predetermined quantity of fresh KOH continuously through feed inletpipe 85 and control valve 86 and to continuously withdraw the spentsolution and precipitate from the outlet pipe 80.

The ore tailings, from which the platinum and gold have been extractedby volatilization flow downwardly, being advanced by auger feed 72,through pipe 70 into the tailings receiver 71.

It is important to regulate the rate at which the hydrochloric acid issupplied through pipe 42 into glass 41 with reference to the rate atwhich the nitric acid is added to pipe 43. The preferred ratio of themixture is three parts of hydrochloric acid to one part of nitric acid.The glass container 41 is warmed by the heater 44 so that the aqua regiais vaporized into nitrosyl chloride and chlorine.

The motors 24, 63 and 73 are preferably connected to the same powercircuit 90, 91 from any suitable source 92, 93 through a double knifeswitch 94. Thus when the switch is closed, all three motors operateconcurrently and continue during the operation of the process which issubstantially continuous. When necessary or desirable to stop theoperation, the switch 94 is opened and all three motors stop.

The arrangement of the apparatus illustrated and above describedconstitutes the best embodiment of my invention now known to me, butother embodiments may be made without departing from the invention.Consequently, only such limitations should be imposed as are indicatedin the appended claim.

I claim:

Apparatus for the separation of platinum from finely divided ores orsands containing the same that comprises a horizontal ceramic tubeconstituting a retort, means for supplying heat at moderate temperatureto said ceramic tube, an outer metal tube of larger diameter, insulatingmaterial around the ceramic tube within the outer metal tube, a helicalauger centered within the ceramic tube, means for continuously supplyingfinely divided ore or sand to the inlet end of the ceramic tube, meansfor slowly rotating the helical auger to feed the ore or sand throughthe tube and agitate it therein, means for passing a mixture of nitrosylchloride and chlorine vapors through the ceramic tube concurrently withand in contact with the ore, a vapor off-take near the top of the outerend of the ceramic tube, a solid off-take near the bottom of the outerend of the ceramic tube, a precipitation tank connected to the vaporofftake, a KOH tank connected to the precipitation tank at the bottom, areturn pipe connected from the KOH tank to the precipitation tank andextending into said tank at the top, means for circulating the KOHthrough the return pipe, and a jet pump connected to receive vapor fromthe vapor otftake and actuated by the KOH circulated through the returnpipe.

References Cited in the file of this patent UNITED STATES PATENTS1,554,972 Merwin Sept. 22, 1925 1,599,372 Reed Sept. 7, 1926 1,806,042Carter May 19, 1931 2,104,741 Fink Jan. 11, 1938 2,238,792 Hanawalt etal Apr. 15, 1941 2,349,747 Muskat May 23, 1944 2,349,801 Maier May 30,1944 2,784,960 Lee Mar. 12, 1957 2,900,236 Speed et a1 Aug. 18, 19593,021,209 Murray et al Feb. 13, 1962

